The long-term goal of the proposed research has changed only slightly in the last year. It is to gain insight into the physiology of epididymal spermatozoa and testicular and epididymal tubules. In particular, we are investigating alterations in the ionic, hormonal and protein contents of the tubule fluid as it flows from the testis through the rete testis, ductuli efferentes, and the epididymis. We are also examining the transport of organic and inorganic compounds into and out of the seminiferous tubules (the blood testis barrier) and the epididymis. This information should help male reproductive physiologists to understand the complex interactions between the sperm and their fluid milieu, sperm maturation, and sperm transport. Goals: 1. To further investigate the epididymal factor(s) which inhibit the initiation of sperm motility. 2. To investigate the concentration and electrophoretic characteristics of proteins in the epididymal and seminiferous tubule lumen. 3. To further analyze the elemental contents of seminiferous and epididymal tubule fluids. 4. To study the effects of in vivo manipulation of sex steroids on '3' above. 5. To study the transport of glucose between blood and luminal fluids in the testis and epididymis. 6. To measure the level of sex steriods in these fluids.